How to not waste my annotated file?

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Hi I am working on a project that will detect cracks using mask rcnn. I wan to implement your code however I already have done annotating my 3,500 images on VGG annotator. I have my json file already. As I looked into your code, I see you have a .py file for annotation tool. In order to train my model with your code, do I need to annotate again? How can I use my .json file to your code? Hoping for a reply. Thank you